It’s kindly of simple to tell apart whether anti-foaming agent added or not.
Here we have below three ways you can try:
Notice:
No special requirement on concentration in below testing, normally 4%. Anti-foaming agent can
works with any concentration.
Please keep the same conditions in the control group

1. Observe the solution after dissolution.
The picture shows PVA sample with oily anti-foaming agent. (whether the water-based AF agent
will reflect this feature remains to be verified)

1788A (with AF agent), AF agent would make the solution muddy and opaque
1788(without AF agent), the solution is transparent as water

2、After proper dissolution, stir the solution and observe the foaming and defoaming conditions

1788, 15mesh, without anti-foaming agent	1788A, 15mesh, with anti-foaming agent
After stirred, there are more bubbles, and the bubbles do not disappear for a certain time	After stirred, a small amount of bubbles will appear, and what can disappear quickly
Foaming will be more obvious if PVA particle size is finer (tested by buyer,2488，mesh size 15-20)

3、 After heating, the performance characteristics of foam will be more obvious

1788A，15mesh，with anti-foaming agent	1788，15mesh. Without anti-foaming agent
After heating to above 90 ℃, a small amount of bubbles will appear, and defoaming will be faster after heating is stopped	After heating to above 90 ℃, foaming is very obvious, and defoaming is slow after stopping heating, the foaming would stay for a certain time